Electric lamps may at times include internal reflectors to shape and direct the light output. By placing the reflector inside the envelope, the reflector is securely and permanently oriented with respect to the filament. There are difficulties with internal reflectors. Reflectors have both size and mass that may interfere with the lamp assembly and filament operation. The reflector must not contact the filament electrically shorting, or mechanically distorting the filament. Sturdy support rods, bridge elements and other structures have therefore been used to control the reflector's position. The support structures are usually secured between two heavy support posts. An example of such internal support structures may be seen in U.S. Pat. No. 3,555,338 to Robert F. Scoledge et al for Incandescent Lamp showing an internal reflector supported on enlarged rods that have bridge elements connecting between the rods. U.S. Pat. No. 4,079,283 to Frederick J. George for High Wattage Incandescent Lamp with Support for a Planar Segmented Filament shows an internal reflector supported by an inner filament lead. The lead is an enlarged "spud" to support the reflector weight. U.S. Pat. No. 4,150,316 to Robert E. Levin et al for Incandescent Projection Lamp with Internal Reflector having Light Defining Opening Therein shows a three panel internal reflector mounted on support rods separated by two bridge elements.
As a result, the envelope requires additional space for the supports. Smaller lamps such as hard glass automotive lamps may contain internal reflectors but the small internal space frustrates deft positioning of the support mechanisms. There is then a need for internal lamp reflectors that do not rely on large support structures.
The lamp seal necessarily includes the electrical connections for the filament. The seal area is generally made small to allow a less expensive base, and a greater view of the filament. Inclusion of support, or other structures in the seal area invites electrical shorts to the reflector supports. Similarly, the envelope seal is weakened by large support members penetrating the seal. The support members likely have different coefficients of thermal expansion than does the envelope. The envelope and support members then do not seal well. The supports necessarily transmit the forces on the reflector to the seal. The forces work the seal, and act to separate the supports from the seal. There is then a need for a reflector support that does not weaken the seal.
A reflector to function ideally, needs to be properly positioned with respect to the filament. Ordinarily, the reflector orientation is kept by controlling the support rods during assembly, but controlling the support rods requires either additional design, labor, or machine precision. There is then a need for internal lamp reflectors that can be easily and accurately positioned during assembly.